By virtue of such features as light weight, small thickness and low power consumption, liquid crystal display devices have been used in various fields as display devices of OA equipment such as a personal computer, a TV, etc. In recent years, liquid crystal display devices have also been used as display devices of a portable information terminal device such as a mobile phone, a car navigation apparatus, and a game machine, etc.
In such liquid crystal display devices, there has been an increasing demand for the improvement of fineness of an image according to an increase in information amount, the improvement of display speed for adaptivity to a moving picture, and the realization of a wider viewing angle. With the advancement in microfabrication of a TFT (Thin Film Transistor) array structure, there have been proposed, as liquid crystal modes which meet such demands, an OCB (Optically Compensated Bend) system using a nematic liquid crystal, a VAN (Vertical Aligned Nematic) system, a HAN (Hybrid Aligned Nematic) system, a it alignment system, an IPS (In-Plane Switching) system, and an FFS (Fringe Field Switching) system.
In particular, the FFS system has already been adopted in various fields as the liquid crystal display mode which realizes a high contrast, a wide viewing angle and a high transmittance. In a characteristic structure of the FFS system, two kinds of transparent electrodes, which are opposed to each other with an insulation layer being interposed, are provided on the same substrate, and a slit pattern is provided on the upper-layer electrode. The alignment of liquid crystal molecules is controlled by controlling an electric field which is produced between the two kinds of transparent electrodes.